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Question on propane use....

Post questions and info about combustion (flammable vapor) powered cannons here. This includes discussion about fuels, ratios, ignition systems, safety, and anything else relevant.
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Question on propane use....

Unread postAuthor: Applegonebad » Sat Dec 19, 2009 4:56 pm

Allright so I live in wisconsin and right now its about 30 degrese. I was just outside dryfireing my gun with a few different propellents so i could find sometihing better for my gun than gumout, becasue I have a PVC launcher, 3 inch diameter chamber thats 2 feet long, and 2 inch diameter barrel thats 3 feet long.. I have allways used gumout, even though I know it breaks down your launcher's plastic.. So one of the things I tried was propane. I made sure the chamber was all clear, and put a reall small shot in there, and it only combusts like 10% of the time... When I try the gumout it will combust 90% of the time, and give TONS of power! But I really like the fact of using propane, and I tried to use a bunch of different amounts, sometimes I would get some nice results but still noting like the gumout.. Whats wrong here? I was thinking of installing a 20mm chamber fan, ive got one sitting here and tonight im going to mount it and see if it helps. Any ideas to why the propane isnt working like people say it does?
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Unread postAuthor: Moonbogg » Sat Dec 19, 2009 4:59 pm

You need to actually measure the right ammount of propane. 4.03% of chamber volume is the target ratio to use. It is picky and needs to be fairly accurate, so your 10% success rate sounds about right for guess work.
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Unread postAuthor: Applegonebad » Sat Dec 19, 2009 5:05 pm

Moonbogg wrote:You need to actually measure the right ammount of propane. 4.03% of chamber volume is the target ratio to use. It is picky and needs to be fairly accurate, so your 10% success rate sounds about right for guess work.


O damn lol, oops, i have seen those funky meters before, how do I go about making one for my gun? Also is engine starter okay to use as fuel in a PVC gun
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Unread postAuthor: kjjohn » Sat Dec 19, 2009 6:05 pm

Go to Burnt Latke's site (you can just google "burnt latke"). It has very good instructions on making a metering device. I suppose engine starter could work, but you couldn't meter it very well, and I doubt it would have as much power as metered propane or MAPP.
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Unread postAuthor: Applegonebad » Sat Dec 19, 2009 6:12 pm

kjjohn wrote:Go to Burnt Latke's site (you can just google "burnt latke"). It has very good instructions on making a metering device. I suppose engine starter could work, but you couldn't meter it very well, and I doubt it would have as much power as metered propane or MAPP.


Thanks a bunch man ill check that site.
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Unread postAuthor: SpudBlaster15 » Sat Dec 19, 2009 6:19 pm

If you don't want to build a meter, a can of starting fluid with the nozzle from a deodorant can (To produce a finer mist) works nearly as well.
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Unread postAuthor: ZRTMWA » Tue Dec 22, 2009 3:57 pm

Also, was the propane can sitting outside for a while? I believe cold temperatures really minimize the amount of pressure you can achieve from propane.
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Unread postAuthor: kjjohn » Tue Dec 22, 2009 7:20 pm

Temperature does make a difference, but it would probably not prevent a metered mix from igniting. The main factor is getting the right stoichiometric, or fuel to air mixture.
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Unread postAuthor: Joshatdot » Wed Dec 23, 2009 12:02 pm

+1 for the Starting Fluid w/nozzle. Plus if you are going to go metered propane, you'll need a chamber fan. But a chamber fan in any combustion cannon is best.
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Unread postAuthor: artillerycreations » Wed Dec 23, 2009 3:13 pm

You wouldnt necessarily need a chamber fan with propane and the fact that your chamber is relatively short would mean that just waiting a few seconds for the propane to mix would do the trick. The main problem i have had with cold weather is fuels condensating on the walls of the chamber. Propane gets rid of all of the mess and glue like residue left on the chamber. It would definately be worth if for you to get a propane setup up and running.
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Unread postAuthor: cfb_rolley » Sat Jan 02, 2010 2:57 am

so what's the power difference between hair spray/ starting fluid/ propane? are there any other fuels you could use?
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Unread postAuthor: jackssmirkingrevenge » Sat Jan 02, 2010 3:03 am

cfb_rolley wrote:so what's the power difference between hair spray/ starting fluid/ propane? are there any other fuels you could use?


Have a look at the Image
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